A water-in-oil type cosmetic has heretofore been used as a skin cosmetic such as a sunscreen cosmetic which is required to have waterproofness. However, since a water-in-oil type emulsion inevitably contains a relatively large amount of an oil component, the emulsion has a problem in texture such as leaving a greasy feeling when applied onto the skin.
Though a volatile oil component is blended in order to improve the greasy feeling of the water-in-oil type emulsion, an emulsion which mainly contains volatile silicone oil as the volatile oil component has marked slippery feel and squeakiness and sometimes impairs appropriate moisturized feeling after application. Further, even though the slippery feel and squeakiness are improved when a volatile hydrocarbon oil component is incorporated into the water-in-oil type emulsion containing the nonvolatile silicone oil, such emulsion has a problem of deterioration in long term stability.
Patent Document 1 describes a transfer resistant cosmetic composition containing a nonvolatile silicone compound and a nonvolatile hydrocarbon oil component which is incompatible with the silicone. The cosmetic contains a volatile hydrocarbon oil component (solvent) in which the nonvolatile hydrocarbon oil component is soluble and the nonvolatile silicone compound is soluble or dispersible. The cosmetic is improved in transfer resistance by specifying a dissolution parameter of the nonvolatile hydrocarbon oil component.
Patent Document 2 describes a water-in-oil type emulsion composition obtained by incorporating a fiber, a silicone surfactant, and clay, which allegedly has good stability at a high temperature (e.g. 45° C.)
Patent Document 3 describes a water-in-oil type emulsified sunscreen cosmetic containing a zinc oxide powder subjected to a special surface hydrophobizing treatment, volatile silicone, polyoxyalkylene-modified organopolysiloxane, and water. It is described that the water-in-oil type emulsified cosmetic may further contain an organic modified clay mineral, and that an emulsion which stably incorporates the powder can be obtained without increasing an oil component such as nonvolatile silicone.
However, in the conventional techniques including Patent Documents 1 to 3, the problem of impairment of stability of emulsion, which can occur when volatile hydrocarbon oil is incorporated into a water-in-oil type emulsion, is not recognized at all, and any countermeasure for the problem is not disclosed nor suggested. Further, a problem of deterioration of compatibleness with the skin caused by incorporation of a silicone oil component has been raised.